1. Field of the Invention
The present invention relates to a seat belt for protecting a vehicle occupant during a vehicle collision and, more particularly, to an inflatable belt capable of being inflated with gas.
2. Description of the Related Art
An inflatable belt device of this type is disclosed in Japanese Unexamined Patent Publication H05-85301 and is shown in FIGS. 6(a) and 6(b). This passenger protective device 1 includes a shoulder belt 2 extending diagonally from the right side to the left side of a passenger, a lap belt 3 extending from the right side to the left side of the passenger, a buckle 4 fixed to, for example, a vehicle floor, a tongue 5 to be inserted into and engaged with the buckle 4 when the passenger wears the belt, and an intermediate guide 6 for guiding the shoulder belt 2.
The shoulder belt 2 includes a webbing 2a, which is the same as a typical conventional seat belt, and an inflatable belt 2b connected to an end of the webbing 2a. The webbing 2a is slidably hung in the intermediate guide 6. The other end of the webbing 2a is connected to a shoulder belt retractor 7 with an emergency locking mechanism (ELR), which is fixed to the vehicle body. The webbing 2a is arranged such that it is wound into the shoulder belt retractor 7.
The inflatable belt 2b is positioned so that it contacts the passenger and is connected to the tongue 5 at an end opposite to the end connected to the webbing 2a. The lap belt 3 is composed of a webbing, which is the same as a typical conventional seat belt, having one end is connected to the tongue 5 and the other end connected to a lap belt retractor 8 (ELR), which is fixed to the vehicle body. A gas generator 9 is connected to the buckle 4. The gas generator 9 is actuated in emergency situations, e.g., vehicle collisions, to generate high-pressure gas. The tongue 5 and the buckle 4 are each provided with passages for introducing gas from the gas generator 9 into the inflatable belt 2b.
The inflatable belt 2b of the shoulder belt 2 includes a belt body 2c formed in an envelope-like shape and a cover 2d. The belt body 2c is folded, shown in solid lines in FIG. 6(b), and then covered by the cover 2d. The ends of the cover 2d are then connected to each other by stitching 2e so that the inflatable belt 2b is maintained in a band-like configuration. The stitching 2e of the cover 2d is easily torn by the force of the shoulder belt 2 expanding when the gas generator 9 is actuated so that the inflatable belt 2b is deployed, shown by a two-dot chain line in FIG. 6(b).
The belt body 2c is made of, for example, rubber coated fabric and the cover 2d is made of a flexible knit with excellent stretchability.
FIGS. 5(a) through 5(d) are perspective views illustrating the manufacturing process of a conventional inflatable belt. Conventionally, two pieces of base fabrics 11, 12 are first cut to correspond to the configuration of a belt body being manufactured. The base fabrics 11, 12 are then superposed on each other (FIG. 5(a)) and sewn together along their peripheries to make an envelope-like or elongated belt body 14 (FIG. 5(b), numeral 13 designates stitching). After that, the belt body 14 is longitudinally folded into a band-like configuration (FIG. 5(c)). Last, the belt body 14 is accommodated in a knit cover 15 (FIG. 5(d)), thereby making the inflatable belt 16.
The belt body 14 made from superposing the base fabrics 11, 12, which were cut in a special configuration to correspond to the configuration of the belt body and then sewn together, includes areas A, B, C, which have different volumes (due to the changing widths of the base fabrics 11, 12). Therefore, the folded body made by longitudinally folding the belt body 14 has a non-uniform thickness. That is, the folded body is thin around both ends and thick around the longitudinal center. Accordingly, the inflatable belt 16, which includes the above folded body and the knit cover 15, also has a non-uniform thickness.
An inflatable belt having such a non-uniform thickness feels poorly to a vehicle occupant when the belt contacts his/her chest and/or abdomen during driving.
The conventional belt body is constructed by sewing substantially the entirety of the peripheries of the superposed base fabrics. As a result, the length of the stitching is long, thus increasing the cost and also decreasing the productivity.
Such long stitching is undesirable not only because of the increased cost and decreased productivity, but also because gas may leak at the sewn portions during inflation and deployment of the inflatable belt.
These difficulties or problems with the current alternatives are not intended to be exhaustive, but are many which tend to reduce the desirability of known seat belts. Other notable problems may exist; those presented above, however, should be sufficient to demonstrate that devices appearing in the past are amenable to worthwhile improvement.